Technologies about efficient use of storage capacity are disclosed in, for example, following patent literatures.
Japanese Unexamined Patent Application Publication No. 2011-248742 (hereinafter referred to as PTL 1) discloses a technology of reducing storage capacity used by a virtual machine. The technology disclosed in PTL 1 extracts a difference between a disk image used by an existing virtual machine and a master disk image used as a master. The technology disclosed in PTL 1 replaces the disk image of the virtual machine by a difference disk image storing the difference.
Japanese Unexamined Patent Application Publication No. 2013-054416 (hereinafter referred to as PTL 2) discloses a technology of reducing physical storage capacity needed for a copy destination of backup data. For each partial area included in a data area in a copy source, the technology disclosed in PTL 2 generates and stores a code used to determine the sameness of data included in the areas. When copying partial areas that store the identical data to data areas in a copy destination, the technology disclosed in PTL 2 assigns an identical physical storage area to the respective partial areas.
Japanese Unexamined Patent Application Publication No. 2006-011811 (hereinafter referred to as PTL 3) discloses a technology of excluding unnecessary data from a managed object in a storage system connected to a host apparatus. The storage system disclosed in PTL 3 includes a primary volume and a difference volume that accumulates differences from the primary volume. The technology specifies a storage area in the primary volume, which is associated with an area not referenced in a file system in the host apparatus. Then, the technology deletes a storage area, in the difference volume, which is associated with the specified storage area in the primary volume.
A technology related to management, operation, and the like of a storage system is disclosed in following patent literatures. These technologies are not directly related to efficient use of storage capacity.
For example, Japanese Unexamined Patent Application Publication No. 2014-032515 (hereinafter referred to as PTL 4) discloses a technology, applied in a storage system which duplicates data via a network, to release part of a storage area including copy target data, while the data are in duplication process.
For example, Japanese Unexamined Patent Application Publication No. 2008-158570 (hereinafter referred to as PTL 5) discloses a technology applied for a storage apparatuses. By the technology, a plurality of storage apparatuses verify sameness of data stored in the respective apparatuses, by generating and interchanging a check code for data stored in the respective local apparatuses. Thus, the technology disclosed in PTL 5 reduces transfer of identical data.